The etiology of sinus tachycardia is mostly functional, but can also be seen in organic heart disease and extracardiac factors. Its production is mainly related to sympathetic excitation and reduced vagal tone. (1) Physiological: Physiological sinus tachycardia is very common, and many factors affect the heart rate, such as position change, physical activity, food digestion, emotional anxiety, pregnancy, excitement, fear, agitation, alcohol, smoking, tea, etc., which can increase the heart rate. In addition, age is also a factor, and children tend to have a faster heart rate. (2) Pharmacological: such as sympathomimetic drugs such as ephedrine and epinephrine. Parasympathetic blocking drugs such as atropine, caffeine, thyroxine, amphetamines, etc. can cause tachycardia. (3) Pathological: such as systemic diseases: hyperthermia, anemia, hypoxia, infection, hyperthyroidism, pain, acute rheumatic fever, foot disease and neurosis can cause tachycardia. (4) Cardiovascular diseases: acute blood loss, hypotension and shock, arteriovenous fistula, heart failure, myocarditis, cardiomyopathy, pericarditis, acute myocardial infarction and various organic heart diseases can cause sinus tachycardia.